Buildbot requires Twisted-11.0.0 or later on the master, and Twisted-8.1.0 on the worker.
In upcoming versions of Buildbot, a newer Twisted will also be required on the worker.
As always, the most recent version is recommended.
Note that Twisted requires ZopeInterface to be installed as well.

Future:

As part of ongoing (but as-yet incomplete) work to make Buildbot compatible with Python 3, the master requires the future module.

Of course, your project's build process will impose additional requirements on the workers.
These hosts must have all the tools necessary to compile and test your project's source code.

Buildbot requires a database to store its state, and by default uses SQLite.
Version 3.7.0 or higher is recommended, although Buildbot will run down to 3.6.16 -- at the risk of "Database is locked" errors.
The minimum version is 3.4.0, below which parallel database queries and schema introspection fail.

Please note that Python ships with sqlite3 by default since Python 2.6.
Python2.6 for Windows ships with sqlite 3.6.2, thus you will not be able to run buildbot with sqlite on Windows and Python 2.6.

If you configure a different database engine, then SQLite is not required.
however note that Buildbot's own unit tests require SQLite.